No Longer On Exam Flashcards
(40 cards)
What is variation?
Differences in the characteristics of individuals in a population is called variation.
What are the causes of variation within a species?
- Genetics.
- Environment.
- A mixture of both genetics and environment.
What is genetic variation?
- Variations in the genotypes of organisms of the same species due to the presence of different alleles.
- Creates differences in phenotypes.
What creates genetic variation in a species?
- Spontaneous mutations.
- Sexual reproduction.
What is a mutation?
A random change to the base sequence in DNA which results in genetic variants. They occur continuously.
State 3 types of gene mutation
- Insertion.
- Deletion.
- Substitution.
How may a gene mutation affect an organism’s phenotype? (3)
- Neutral mutation does not change the sequence of amino acids. Protein structure and function are the same. No effect on phenotype.
- Mutation may cause a minor change in an organism’s phenotype such as change in eye color.
- Mutation may completely change the sequence pf amino acids. This may result in a non-functional protein and can cause severe changes in phenotype.
What is the consequence of a new phenotype caused by a mutation being suited to an environmental change?
There will be a rapid change in the species.
What is evolution?
- A gradual change in the inherited traits within a population over time.
- Occurs due to natural selection which may lead to the formation of a new species.
Outline the theory of natural selection
All species of living things have evolved from simple life forms that first developed more than 3 billion years ago.
1) Genetic variation exist due to spontaneous mutations.
2) Selection pressures such as competition and disease exist.
3) Random mutation gives an organism a selective advantage.
4) Organism is better adapted to the environment and survives.
5) Organism reproduces, passing on its beneficial alleles.
6) Frequency of advantageous alleles increase.
How do 2 populations becomes different species?
When their phenotypes become different to the extent that they can no longer interbreed to produce fertile offspring.
What is selective breeding?
The process by which humans artificially select organisms with desirable characteristics and breed them to produce offspring with similar phenotypes.
Outline the main steps involved in selective breeding
1) Identify a desirable characteristic such as disease resistant.
2) Select parent organisms that show the desired traits and breed them together.
3) Select offspring with the desired traits and breed them together.
4) Process repeated until all offspring have the desired traits.
Give example of characteristics selected for in selective breeding
- Disease resistance in crops.
- Higher milk or meat production in animals.
- Gentle nature in domestic dogs.
- Large flowers.
What is the main advantages of selective breeding?
Creates organisms with desirable features:
- Crops produce a higher yield of grain.
- Cows produce a greater supply of milk.
- Plants produce larger fruit.
- Domesticated animals.
Other than in agriculture, where is selective breeding useful?
- In medical research.
- In sports such as horse racing.
Outline the disadvantages of selective breeding (4)
- Reduction in the gene (which becomes especially harmful if sudden environmental change occurs).
- Inbreeding results in genetic disorders.
- Development of other physical problems such as respiratory problems in bulldogs.
- Potential to unknowingly select harmful recessive alleles.
What is genetic engineering?
- The modification of the genome of an organism by the insertion of a desired gene from another organism - genes from chromosomes of humans and other organisms can be ‘cut out’ and transferred to cells of other organisms.
- Enables the formation of an organisms with beneficial characteristics.
Give an example of uses for genetically modified plants
- Disease resistance.
- Produce larger fruits.
What is a use for genetically modified bacteria cells?
To produce human insulin to treat diabetes.
Describe the benefits of genetic engineering (3)
- Increased crop yield for growing populations such as herbicide resistant and disease resistant.
- Useful in medicine such as insulin-producing bacteria.
- GM crops produce scarce resources such as GM golden rice producing beta-carotene (source of vitamin A in body).
Describe the risks of genetic engineering (4)
- Long term effects of consumption of GM crops unknown.
- Negative environmental impacts such as reduction in biodiversity, contamination of non-GM crops forming ‘superweeds’.
- Late-onset health problems in GM animals.
- GM seeds are expensive. LICs may not be able to afford them or may become dependent on businesses that sell them.
What is the name for crops that have had their genes modified?
Genetically modified (GM).
What is Bacillus thuringiensis (Bt)?
- Insect larvae are harmful to crops.
- Bt is a bacterium which secretes a toxin that kills insect larvae.
